Inflatable earplug system

ABSTRACT

A deep insert, inflatable hearing protection earplug is provided that is easy for an untrained user to insert correctly, reliably providing high acoustic attenuation and remaining both secure and comfortable for long durations in a human ear. The earplug comprises a soft elastomer shell that forms a sealed volume filled with an inert fluid. The earplug can comprise a slender, flexible stem that is easily insertable into the ear canal when deflated. The proximal end of the earplug can be situated outside the ear canal, within the concha of the ear, and incorporates a bulb with a hemispherical, bistable cap. After inserting the shaft of the earplug into the ear canal, the wearer applies force with a finger to invert the cap, which transitions elastically from a convex to a concave external geometry, displacing a fixed volume of fluid to inflate a sheath that forms the outer covering of the stem, filling and sealing the ear canal. The sheath can be deflated by pulling on or otherwise engaging a release tab or other feature attached to the cap.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and the benefit of U.S.Provisional Patent Application No. 63/138,433, filed Jan. 16, 2021,which is fully incorporated herein by reference.

FIELD

The present invention relates generally to hearing protection devicesand, more particularly, to an inflatable earplug system and device thatis comfortable and easy for an untrained user to fit and remove, andwhich produces a high-attenuation acoustic seal deep in the ear canal.

BACKGROUND

Hearing protection is needed by those engaged in occupations oractivities involving loud intermittent or sustained noise. Insufficientprotection in loud noise environments can lead to permanent hearingdamage with related hearing loss or tinnitus. Hearing damage negativelyaffects communication, job performance, and quality of life, and resultsin increased health care costs.

There are many earplugs and earmuffs on the market that attempt toreduce or eliminate the potential damage noisy environments can have onthe human ear. Conventionally, high levels of noise attenuation requirelarge earmuffs, which are bulky, and can be uncomfortable to wear, ordeeply inserted earplugs, which can be difficult and painful to insertproperly. Poorly fitted devices that do not seal to the head or in theear canal at sufficient depth provides low levels of attenuation,leaving the user at risk of hearing damage. If a hearing protectiondevice is not easy to fit correctly and comfortable, it will not be usedor, if used, it will not be effective.

As a result, there is a need for a new and improved earplug system anddevice that solves the innate functional and design flaws ofconventional configurations, designs, and approaches.

SUMMARY

Embodiments of the present invention include an earplug system anddevice that forms a high-attenuating acoustic seal deep in the earcanal, is comfortable, easy for an untrained user to fit and use,intrinsically adaptable to the broad variety of human ear canalanatomies, and secure for long term wear in active environments, whilestill being easily removable when desired. The earplug device provides areliable acoustic seal past the second bend of the ear canal, which willensure high attenuation.

The earplug comprises a soft elastomer shell that forms a sealed volumefilled with an inert fluid. The earplug can comprise a slender, flexiblestem that is easily insertable into the ear canal when deflated. Theproximal end of the earplug can be situated outside the ear canal,within the concha of the ear, and incorporates a bulb with ahemispherical, bistable cap. After inserting the stem of the earpluginto the ear canal, the wearer applies force with a finger to invert thecap, which transitions elastically from a convex to a concave externalgeometry, displacing a fixed volume of fluid to inflate a sheath thatforms the outer covering of the stem, filling and sealing the ear canal.The sheath can be deflated by pulling on or otherwise engaging a releasetab or other feature attached to the cap.

Another object of the invention is to provide such an acoustic seal thatoptionally incorporates an internal air channel for desirablepass-through acoustics. Various filters may be inserted in this channelto affect the frequency-dependent and level-dependent attenuation of theearplug.

Another object of the invention is to provide an earplug device thatcreates such a seal but is readily manufacturable and durable for manyuses over extended periods of time, leading to low overall costs.

The slender stem with a soft, fluid-filled, elastic sheath enables auser to easily insert deep into the ear canal and then inflate manually.The sheath expands, conforming to the inner profile of the ear canal,and produces an acoustic seal with large surface area at uniformpressure. The constant-pressure conformability of the sheath provides acomfortable and uniform seal deep in the ear canal without pressurepoints that can cause discomfort. Further, the large contact surface ofthe area securely anchors the earplug within the ear.

The high acoustic impedance of the fluid that fills the sheath relativeto air results in low transmission of ambient sound. The centralstabilizing core constrains the inflation of the sheath in the axialdirection, ensuring radial inflation, and damps axial oscillation of thefluid volume that might otherwise allow transmission of low frequencysound. The core also provides for the possibility to incorporate theinternal pass-through acoustic channel.

Attached to the distal end of the sheath, the bistable hemisphericalbulb forms a sealed volume filled with fluid. The bulb provides areservoir for the fluid when the sheath is deflated. The bulb is anelastomeric hemisphere that is mechanically stable in either a concaveor convex topology. When the bulb is inverted by force from the user'sfinger, a fixed volume of fluid is displaced and forced into the sheath.The geometry and material of the bulb are selected to provide theappropriate displaced volume for inflation of the sheath, and to retainthe required inflation pressure without inadvertent inversion. The bulbcan also incorporate a tab as an integrally molded component. To removethe earplug, the user grasps the tab and pulls, first inverting the bulbto release the inflation pressure, then continuing to extract thedeflated earplug from the ear.

The geometry of the sheath is tailored to provide advantageous inflationbehavior. The sheath is thinnest near its tip, ensuring that the onsetof inflation and sealing occurs deep in the ear. The wall thickness ofthe sheath is tapered, increasing toward the bulb and outer ear.Inflation initiated at the tip will progress gradually outward towardthe bulb with steadily increasing pressure as fluid is transferred fromthe bulb into the sheath. This allows ear canals of various sizes to beaccommodated with a single earplug design. Large diameter ear canalswill seal with greater radial expansion at the tip of the sheath and ashorter inflated region and seal in the axial direction. Small diameterear canals will seal with less radial expansion and a longer or largerinflated region progressing axially along the stem toward the outer ear.The sheath is sufficiently thick, or very thick, in the concave regionadjacent to the bulb to ensure that this portion does not inflate.

The above summary is not intended to describe each illustratedembodiment, claimed embodiment or implementation of the invention. Thedetailed technology and preferred embodiments implemented for thesubject invention are described in the following paragraphs accompanyingthe appended drawings for people skilled in this field to wellappreciate the features of the claimed invention. It is understood thatthe features mentioned hereinbefore and those to be commented onhereinafter may be used not only in the specified combinations, but alsoin other combinations or in isolation, without departing from the spiritand scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 shows an isometric view of an inflatable earplug system or devicein a nominal state prior to insertion, in accordance with embodiments ofthe present invention.

FIG. 2A shows an isometric view of a core of an inflatable earplugsystem or device, in accordance with embodiments of the presentinvention.

FIG. 2B shows an isometric view of a sheath of an inflatable earplugsystem or device, in accordance with embodiments of the presentinvention.

FIG. 2C shows an isometric view of a bi-stable cap of an inflatableearplug system or device, in accordance with embodiments of the presentinvention.

FIG. 3A shows an orthographic view of an inflatable earplug system ordevice in the same nominal state as FIG. 1, in accordance withembodiments of the present invention.

FIG. 3B shows a detail section view of the inflatable earplug system ordevice along cross-section A-A of FIG. 3A, in accordance withembodiments of the present invention.

FIG. 4A shows an orthographic view of an inflatable earplug system ordevice in an inflated state, in accordance with embodiments of thepresent invention.

FIG. 4B shows a detail section view of the inflatable earplug system ordevice along cross-section A-A of FIG. 4A, in accordance withembodiments of the present invention.

FIG. 5 shows a detail section view of a cap of an inflatable earplugsystem or device, in accordance with embodiments of the presentinvention.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings, are not intended to be to scale, and will be described indetail. It should be understood, however, that the intention is not tolimit the invention to the particular embodiments described. On thecontrary, the invention is to cover all modifications, equivalents, andalternatives falling within the spirit and scope of the invention asdefined by the appended claims.

DETAILED DESCRIPTION

The system and device of the present invention, shown in FIG. 1, is aninflatable hearing protection earplug 100 comprising a stem 102 that isinserted into a user's ear canal and a bulb 101 that protrudes fromtheir ear canal. The length of the stem 102 should be commensurate withthe typical depth of the human ear canal, typically in the range of0.5-1.0 inches. It may be advantageous to provide multiple (e.g., two orthree) different standard sizes of earplugs with different stem lengthsto accommodate different ear sizes.

In various preferred embodiments, the earplug 100 components or partsare made of molded silicone materials. Silicones are chemically inert,bio-compatible, durable, elastic, resilient, easily molded to intricateshapes by several different processes, readily bonded togetherpermanently with silicone adhesives, and available in a variety offormulations with a large range of durometer hardness, elongation, andother critical mechanical properties. Particular silicone formulationsare selected with mechanical properties beneficial to the function ofeach specific component or part. It should be understood thatalternative embodiments might employ other elastomeric materials,including but not limited to urethanes, nitriles, or latex rubber.

Referring to FIGS. 2A-2C, the earplug 100 is assembled from threeprimary components or parts: a core 103, a sheath 104, and a bi-stablecap 105.

The method by which these components are assembled to form the stem 102and the bulb 101 is evident in the section views of FIGS. 3A-3B—e.g.,showing the earplug 100 in a deflated state with a fluid 111 stored inthe volume of the bulb 101. The sheath 104 is in operative fluidcommunication with the fluid volume 111 in the bulb 101 via one or morechannels, transmission paths or like features between the sheath 104 andthe core 103 at the interface 103 a, as shown in FIG. 3B. The stem 102is formed by overmolding or otherwise assembling the sheath 104 onto thecore 103. During use, the sheath 104 inflates to seal the ear canal. Thefunctions of the core 103 are: to give the stem 102 stiffness whiledeflated and being inserted into the ear canal; to constrain the axialextension of the sheath 104 into the ear canal as it is inflated,preventing pain or damage to the eardrum; to damp axial motion of theinflated sheath that otherwise might transmit low frequency sound; and,optionally, to provide the isolated air channel 106 for pass-throughsound.

The sheath 104 is fixed to the core 103 at either end using adhesive andpossibly anchoring features such as those shown at the tip or endportion 107 of the core 103 to prevent leakage, and at the base 108 toprevent axial elongation. The sheath 104 is free to separate from thecore surface 109 between these features when inflated. The core 103includes an o-ring type groove 107 a to improve adhesion at the tip 107.The anchors 108 include a ridge or groove for the same reason. Inpreferred embodiments, this adhesion is achieved throughsilicone-on-silicone bonding while overmolding the sheath 104 onto thecore 103 or through adhesive if otherwise assembled.

The core 103 is made of a silicone with intermediate durometer hardness,giving it flexibility for insertion, but enough stiffness to resistextension under inflation and dynamic pressures and to resist collapseof the acoustic channel when the earplug is inflated. In variouspreferred embodiments, the core 103 is constructed of a silicone rubberwith durometer hardness of 40 on the Shore A scale.

The material of the sheath 104 should have very low durometer hardnessand high elongation, allowing it to inflate like a balloon and strainseveral hundred percent at low pressure, preferably below 2 pounds persquare inch (PSI). In a preferred embodiment, the sheath 104 isconstructed of a silicone rubber with durometer hardness of 10 on theShore A scale and elongation at break in excess of 400%.

The bulb 101 serves to seal the predefined fluid volume and provide amechanism for displacing fluid to inflate the sheath 104. In variouspreferred embodiments, the bulb 101 incorporates a bistablehemispherical cap 105 for the latter function and assumes a convex shapebefore inflation of the earplug 100. The bulb 101 is formed by adheringthe bi-stable cap 105 to the outer face of the sheath's flange 110. Thesealed volume within the bulb 101 formed by the cap 105 and the sheath104 is filled with unpressurized fluid 111, which may be air, water,oil, or other fluids. It will be understood by one skilled in the artthat various other designs, materials, and constructions could achievethe same objectives consistent with the disclosure provided herein. Thebulb 101 or cap 105 can include a diaphragm, one or more bellows, avalve, or a pump to facilitate fluid displacement.

In use, the narrow stem 102 of the deflated earplug is inserted into auser's ear until the flange 110 is seated against the ear canal opening,providing a fixed and repeatable insertion depth. The user then pressesthe bi-stable cap 105, forcing fluid 111 from the bulb 101 into thesheath 104 until the cap 105 is inverted or otherwise defines a concaveshape (or approaches an inverted or concave shape) and the sheath 104 isinflated.

Referring to FIGS. 4A-4B, section views of the earplug 100 in aninflated state are shown. The thickness of the sheath 104 varies fromthinnest at the earplug tip or end portion 112 to thickest at the flange110. Pressurized fluid 111 squeezed from the bulb 101 will pass throughchannels or unsealed transmission paths between the sheath 104 and thecore 103 or will otherwise separate the sheath 104 from the core 103,creating an interstitial space 113 through which the fluid 111 will flowuntil it reaches the tip 112, where the sheath 104 is thinnest and whereit will first inflate. This important aspect of the design ensures theearplug 100 will first create a seal at the tip 112, which is located inthe deepest portion of the ear canal.

As the sheath 104 at the tip 112 expands in the radial direction, theincreased pressure required for further expansion will begin to inflatethe increasingly thicker sheath 104 away from the tip 112, and theinflated region will grow in the axial direction toward the flange 110.As a result, air is forced out of the ear canal, rather than inward, asthe earplug sheath 104 inflates. This action prevents pressurization ofthe sealed portion of the ear canal, which could otherwise create anunbalanced pressure force against the ear drum, causing pain.

When the earplug 100 is inflated in an ear canal, radial expansion atthe tip 112 is constrained by the canal walls and a seal is formed.Further inflation will then increase the seal contact area. Thus,tapering of the sheath 104 thickness ensures the earplug 100 will createan effective seal in ear canals of varying diameter. In wide ear canals,the radius of the inflated sheath 104 at the tip 112 will be larger andthe axial length of the inflated region will be less than in narrow earcanals, which will have a smaller inflation radius and longer axialregion of inflation to accommodate the same volume of inflation fluid.To keep inflation pressure low and provide good conformability to theear canal, the wall thickness of the sheath 104 near the tip 112 must bevery thin, preferably in the range of 0.002-0.006 inches. The thicknessof the sheath 104 at the flange 110 should be greater, preferably in therange of 0.010-0.050 inches.

An acoustic channel 106 through the core 103 and the flange 110 providesa pass-through by which sounds may be introduced past the earplug seal.Various filters may be inserted in this channel to affect thefrequency-dependent and level-dependent attenuation of the earplug.

To withdraw the earplug 100, the user pulls on the release tab 114 topop the cap 105 into its original convex or non-inverted form. Thisaction will suck fluid 111 back into the bulb 101 and deflate the sheath104. The earplug 100 may then be pulled from the user's ear canal.

Referring to FIG. 5, the bi-stable cap 105 provides a simple andeasy-to-use mechanism and methodology for the user to inflate the sheath104 and ensure that it remains inflated during use. The cap 105 isdefined by geometric features for various preferred embodiments,including a flat land 115 for adhering to the flange 110, a thin elastichinge region 116 to enable inversion, and a hemispherical region 117 ofuniform thickness. The cap 105 is preferably molded as a singlecomponent in its externally convex configuration and including therelease tab 114. The angle T between the tab 114 and an end portion ofthe hemispherical region 117 is important to the bistable function andoperation of the cap 105 and is predefined appropriately, with apreferred value in the range of 20-30 degrees.

The cap 105 geometry is carefully tuned to achieve elastic stability inboth concave and convex topologies, preferably with maximal stability inthe concave case in order to resist the inflation pressure and avoidinadvertent release during use. In the preferred embodiment, the cap 105resists between 2 and 3 PSI in that position. To achieve thisperformance, the cap 105 is preferably constructed of a relatively stiffsilicone with durometer hardness of 60 on the Shore A scale. Thissilicone should also have high elongation capability to enableresilience and durability in the elastic hinge region 116. The inversiondisplacement of the cap 105 is matched to the sheath inflation volumerequired to achieve a good seal in the ear canal. In various preferredembodiments, the inversion displacement of the cap 105 is in the rangeof 0.025-0.050 cubic inches. In certain embodiments, it may beadvantageous to provide multiple (e.g., two or three) different standardsizes of earplugs 100 with different displacement volumes to accommodatevarious ear sizes.

For a highly attenuating earplug 100, it is desirable for the earpluginflation fluid 111 to have acoustic impedance (the product of densityand sound speed) which differs significantly from that of air. Mostcommon liquids meet this requirement.

It is also beneficial to select a liquid with low vapor pressure. Allsilicones have high permeability, and the liquid tends to diffusethrough the silicone sheath 104. A liquid with higher vapor pressure(such as water) tends to evaporate from the outer surface of the sheath104. This evaporation maintains a concentration gradient across thesheath 104, driving further diffusion and ultimately depleting thevolume of liquid contained in the earplug 100 over time. A liquid withlow vapor pressure will still diffuse through the sheath 104 but willnot evaporate when reaching the outer surface. This brings diffusion toa halt and prevents significant depletion of the liquid volume. Thisdiffusive process also maintains a thin layer of liquid on the exteriorof the sheath 104, providing a slight lubrication effect which can bebeneficial to the function and comfort of the earplug.

Further, it is important for the fluid 111 to be inert andbiocompatible. It should be safe for contact with the ear canal as aresult of diffusion, or in the case of a leak or rupture of the sheath104. In certain preferred embodiments, these requirements are met withliquids such as glycerol, mineral oil, or silicone oil. In alternativeembodiments, other liquids might also be used.

In another embodiment, the earplug fluid 111 may be a gas instead of aliquid. Experimental data show that such a gas-filled earplug providesmodest sound attenuation, but a very flat frequency response. This maybe beneficial for some applications. For example, musicians arechronically exposed to high sound levels during performance and wouldbenefit from some level of hearing protection, without sacrificingacoustic fidelity.

In the various preferred embodiments of the invention, the threeelastomer components of the earplug 100, e.g., the core 103, the sheath104, and the bi-stable cap 105, are fabricated efficiently by moldingusing two-part liquid silicone, heat cured liquid silicone, or heatcured high consistency silicone rubber. The core 103 is molded first,then the sheath 104 is over-molded onto the core 103. This overmoldingprocess naturally forms the required mechanical attachment and seal atthe tip 107 of the sheath 104 and the anchor points 108. The requiredrelease between the sheath 104 and the core 103 at the tapered interface109 is achieved by applying a mold release agent to that surface of thestem 102 prior to the overmolding process. These steps will be readilyunderstood by one skilled in the art of molding.

Alternatively, the sheath 104 may be formed separately from the core 103by a process such as injection molding or dip molding and may then beassembled onto the core with adhesive being applied to seal the tip 107and anchor the base 108.

The cap 105 can be formed separately by simple injection molding. It isthen permanently adhered to the open end of the sheath 104 with anappropriate adhesive.

The fluid 111 can be introduced into the sealed volume after the cap 105is adhered by injection with a hypodermic needle through the thick,spherical portion of the sheath 104. Any gas bubbles remaining in thesealed volume can be extracted with the same hypodermic needle after thecorrect volume of liquid has been injected. When the sheath 104 is madeof a soft silicone material and the hypodermic needle is small gauge andsharp, and the injection site is substantially self-sealing and does notresult in a leak after the needle is removed. Alternatively, the fluid111 may be introduced before the cap 105 is adhered by using an externalvacuum to inflate the sheath 104 at the stem 102. The fluid 111 willfill the inflated region 104 and the cap 105 may be adhered in itsconcave form. Other methods are also possible.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof, and it is,therefore, desired that the present embodiment be considered in allrespects as illustrative and not restrictive. Similarly, theabove-described methods and techniques for providing and using thepresent invention are illustrative processes and are not intended tolimit the methods of manufacturing the present invention to thosespecifically defined herein. Further, features and aspects of thevarious embodiments described herein can be combined to form additionalembodiments within the scope of the invention even if such combinationis not specifically described herein.

What is claimed is:
 1. An inflatable hearing protection device,comprising: a longitudinal central core element; an expandable sheathshrouding and anchored to the central core element, wherein theexpandable sheath includes a proximal end portion and a distal endportion; and a cap element in operative fluid communication with theproximal end portion of the expandable sheath, wherein the cap elementcontains a volume of a fluid and is configured to invert from agenerally convex shape to a generally concave shape to adjustablydisplace the fluid to inflate the distal end portion of the expandablesheath to facilitate an acoustic ear canal seal.
 2. The device of claim1, wherein the expandable sheath is constructed at least in part of anelastomer to facilitate inflatable expansion.
 3. The device of claim 2,wherein the elastomer expands at pressure below two Pounds per SquareInch (PSI).
 4. The device of claim 1, wherein the expandable sheathincludes a wall having a tapered thickness.
 5. The device of claim 4,wherein the tapered thickness of the wall increases from the distal endportion to the proximal end portion of the expandable sheath.
 6. Thedevice of claim 1, wherein the longitudinal central core element isanchored to the expandable sheath at the distal end portion tofacilitate controlled inflation of the expandable sheath.
 7. The deviceof claim 1, wherein the longitudinal central core element includes oneor more isolated air channels to facilitate pass-through sound.
 8. Thedevice of claim 1, wherein the fluid has an acoustic impedance differentthan air.
 9. The device of claim 1, wherein the fluid includes aglycerol, a mineral oil, or a silicone oil.
 10. The device of claim 1,wherein the fluid includes a gas.
 11. The device of claim 1, wherein theexpandable sheath includes a flange to facilitate seating.
 12. Thedevice of claim 1, wherein the cap element is manually manipulated todisplace the fluid.
 13. The device of claim 1, wherein the cap elementincludes a diaphragm, one or more bellows, a valve, or a pump.
 14. Thedevice of claim 1, wherein the cap element is a bistable hemisphericalbulb element.
 15. The device of claim 1, wherein a geometry of the capelement is configured to resist at least 2 PSI of inflation pressure.16. The device of claim 1, wherein the cap element includes a releasetab to release inflation pressure.
 17. The device of claim 1, whereinthe expandable sheath is constructed of a low durometer elastomer andthe cap element is constructed of a high durometer elastomer.
 18. Aninflatable hearing protection device, comprising: a central coreelement; an expandable sheath constructed of an elastomer, shrouding andanchored to the central core element, wherein the expandable sheathincludes a proximal end portion and a distal end portion such that atapered wall thickness of the expandable sheath increases from thedistal end portion to the proximal end portion; and a bistablehemispherical cap in operative fluid communication with the proximal endportion of the expandable sheath, wherein the bistable hemispherical capcontains a volume of a fluid and is configured to invert from agenerally convex shape to a generally concave shape to adjustablydisplace the fluid to inflate the expandable sheath to facilitate anacoustic ear canal seal.
 19. The device of claim 18, wherein the centralcore element is anchored to the expandable sheath at the distal endportion to facilitate controlled inflation of the expandable sheath. 20.The device of claim 18, wherein the central core element includes one ormore isolated air channels to facilitate pass-through sounddisplacement.
 21. The device of claim 18, wherein the bistablehemispherical cap includes an elastic hinge region to facilitateinversion of the bistable hemispherical cap.
 22. The device of claim 18,wherein the bistable hemispherical cap includes a diaphragm, one or morebellows, a valve, or a pump.
 23. The device of claim 18, wherein thebistable hemispherical cap includes a release tab to release inflationpressure.